Tales from Kenyon Biology

The Very Hungry Hornworms

This week, intro bio lab students geared up for their Manduca sexta dissection. These tobacco hornworms had grown significantly since students placed them in their plastic “bachelor pad” cages last week. While all hornworms at least doubled in size, the largest of the group were almost 100 times their weight from last week. Thank goodness that’s pretty impossible for humans to do or Kenyon would need to invest in a better health plan now that Marco’s Pizza accepts K-Cards.

Hornworm fact #2: After a good chomp on a tobacco leaf, Manduca have “toxic halitosis” aka poisonous bad breath from the nicotine which deters spiders from eating them.

Hornworm fact #3: Adult Manduca hawkmoths can eavesdrop on the sonar clicks of bats and drop out of the air to avoid being bat food.

If you know the story of The Very Hungry Caterpillar by Eric Carle, the life of a Manduca is quite similar. Rather than eating sausages and ice cream turning into a beautiful butterfly, though, Manduca hornworms eat the leaves of tobacco, tomatoes and other members of the nightshade family (Solanaceae), then metamorphose into a hawkmoth that can hover like a hummingbird. Reared in the lab, however, the Manduca is a beloved model organism with ease of care, rapid growth rate, and accessible anatomy.

This year, the bio lab sections are testing the effect of diet nutrition on overall growth of the organism. Some Manduca will have less nutrition per bite in their food for 48 hours, perhaps affecting how much they eat, absorb nutrients, or grow in a 48 hour period. After this diet change, students hit the microscopes to investigate.

Manduca leg

Spiracles and fat bodies

Malpighian tubules and midgut

Ganglion

Nerve cord

Malpighian tubules and midgut

Nerve cord

Malpighian tubules and midgut

Whether they named their Manduca after their TA (shoutout to Jeremy Moore ’19), took beautiful anatomical pictures under the microscope (see above), or made a video in their hornworm’s honor like Patrick Olmstead ’21 (below), students found a way to connect with their lab-reared pe(s)ts.